Question

I, reservatorio contem 500litros de agua e efetuamos sucessivamente as seguintes operaçoes retiramos 80 litros colocamos 45 litros colocamos 30 litros retiramos 130 litros retiram os 80 litros qual a quantidade de agua que ficou no reservatorio

Answer 1

$500 - 80 = 420$
$420 + 45 = 465$
$465 + 30 = 495$
$495 - 130 = 365$
$365 - 80 = 285l$

Answer 2

$\tt \acute{A}gua=a\\\\\\\tt a=500-80+45+30-130-80\\\\\\\tt a=420+45+30-130-80\\\\\\\tt a=465+30-130-80\\\\\\\tt a=495-130-80\\\\\\\tt a=365-80\\\\\\\to \boxed{\tt a=285}$